ES2484695T5 - Disposable diaper that has a reduced joint between the absorbent core and the backing sheet - Google Patents

Description

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DESCRIPTION

Disposable diaper having a reduced joint between the absorbent core and the backing sheet Field of the invention

The present invention relates to a disposable diaper having absorbent cores comprising superabsorbent polymer particles that are immobilized by an adhesive. The absorbent core is attached to the backing sheet of the disposable diaper only in some joining areas to reduce the view therethrough and the formation of tension lines in the backing sheet.

Background of the invention

The use of superabsorbent polymer material in disposable diapers is well known. The use of superabsorbent polymer material facilitates that disposable diapers have a thinner absorbent core compared to the use of absorbent materials such as frayed pulp, especially when the disposable diaper is in the dry state.

At present, most commercial disposable diapers still have absorbent cores that contain a mixture of so-called air felt (cellulose fibers) and superabsorbent polymer particles. Cellulose fibers composed of the absorbent core generally hold the superabsorbent polymer particles in place since the cellulose fibers entangle the particles so that the particles are trapped between the cellulose fibers. This usually does not result in complete immobilization of the superabsorbent polymer particles, since the particles may have some degree of freedom to move inside the interstices between the cellulose fibers. However, the superabsorbent polymer particles are maintained in the desired position to a sufficiently satisfactory degree.

The use of larger amounts of superabsorbent polymer particles is desirable since it allows for finer absorbent cores. However, when large amounts of superabsorbent polymer particles having little or no air felt are available, the superabsorbent polymer particles are no longer held in place in the interstices between cellulose fibers, since the relationship between The superabsorbent polymer particles and cellulose fibers are too high. Therefore, in absorbent cores that have very high amounts of superabsorbent polymer particles (such as> 80%), the particles must be immobilized by any other means. One way to facilitate immobilization is the use of adhesive, such as hot melt adhesive. The hot melt adhesive can be applied as a thin, fibrous web within the absorbent core. In addition, in absorbent cores that have a high percentage of superabsorbent polymer material and little or no air felt, the superabsorbent polymer material is frequently located between carrier substrates. Carrier substrates are typically nonwoven bands.

Absorbent cores that have relatively high amounts of superabsorbent polymer particles immobilized by hot melt adhesive and that have little or no air felt have little to no gap (eg those provided between cellulose fibers). Thus, there is no "free space" available inside the absorbent core in which the superabsorbent polymer particles can expand after liquid absorption. In these absorbent cores, the superabsorbent polymer particles, after their swelling, will exert a certain force on the nonwoven webs, which normally wind and encompass the superabsorbent polymer particles. Accordingly, the nonwoven webs will also be lengthened to achieve the additional space necessary for swelling of the superabsorbent polymer particles within the absorbent core.

It has been found that an elongated and somewhat stretched absorbent core, when incorporated into a disposable diaper that has been attached to a carrier, can result in a stressed aspect of the backing sheet, leading p. ex. to the formation of tension lines or wrinkles. Such a stressed aspect may cause concerns to the bearers or - if the bearers are babies or young children - to the caregivers regarding the overall quality and especially the capacity of the disposable diaper. The tensioned appearance can be perceived as an indication that the disposable diaper has reached its maximum load and should be changed even if a considerable amount of absorption capacity remains available. Caregivers or carriers may therefore try to change the diaper even if the absorbent core still has the ability to absorb more urine.

Therefore, there is a need for disposable diapers with absorbent cores that have a large amount of superabsorbent polymer particles and little or no air felt, where, when only partially filled with liquid, the backing sheet does not look stressed, especially when it adheres to a carrier.

In US-2007/0123834 A1 an absorbent article is described which has an outer cover, liner and absorbent core which are, each of them, stretchable or extensible. The article has a thickness of about 4 mm or less, and a flexural stiffness of less than about 6 N-mm. The tension in the elastic waist, elastic of the fins and / or elastic of the legs can be modified to adapt to the addition of a more flexible absorbent core. The flexural rigidity of the fasteners can be reduced to further accommodate the improved flexibility of the entire article.

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US-2010/0051166 A1 refers to a method for making a disposable absorbent core comprising depositing absorbent polymer particles from a plurality of deposits in a stamping roller on a substrate disposed in a grid of a support that includes a plurality of rods transverse that extend substantially parallel and separated from each other, to form channels that extend between the plurality of transverse rods.

Summary of the invention

The invention relates to a disposable diaper comprising a backing sheet, a top sheet and in between of the above an absorbent core. The absorbent core has a longitudinal direction with a longitudinal axis and perpendicular thereto a lateral direction with a transverse axis, and the absorbent core also has a front region, a rear region and a crotch region between the foregoing and a front side edge , an opposite rear front edge, and extending longitudinally along the side edges.

The absorbent core comprises superabsorbent polymer particles, which are immobilized by a first adhesive core. The absorbent core comprises one or more elongated channels that are free of superabsorbent particles. The absorbent core is attached to the backing sheet according to one of the following options:

The absorbent core is attached to the backing sheet of the disposable diaper in joining areas adjacent to the front side edge and rear side edge of the absorbent core and the absorbent core is not attached to the backing sheet in any other region; or

The absorbent core is attached to the disposable diaper backing sheet in the crotch region of the absorbent core in one or more joint zone (s) on or adjacent to the longitudinal axis of the absorbent core, wherein the one or more of a junction zone (s) cover 0.2% to 3% of the total surface area of the absorbent core, and the absorbent core is not attached to the backing sheet in any other region; or the absorbent core is attached to the backing sheet of the disposable diaper in the crotch region of the absorbent core in the joint areas adjacent to the longitudinal side edges of the absorbent core and the absorbent core is not attached to the backing sheet in no other region; or

The absorbent core is attached to the backing sheet of the disposable diaper in combinations of any of the joining areas a) to c) and the absorbent core is not attached to the backing sheet in any other region.

The backing sheet is non-elastic and consists of a film and optionally one or more nonwoven webs and where the weight of the backing sheet including the film and optional nonwoven webs is less than 50 g / m2 and where the film has a weight of 10 g / m2 to 20 g / m2.

Brief description of the drawings

Fig. 1 is a plan view of a schematic drawing of a disposable diaper according to an embodiment of the present invention.

Fig. 2 is a cross-section of the disposable diaper shown in Fig. 1 along sectional line 2-2 of Fig. 1.

Fig. 3 is a schematic partial cross-section of an absorbent core layer according to an embodiment of the present invention.

Fig. 4 is a schematic partial cross-section of an absorbent core according to an embodiment of the present invention.

Fig. 5 is a schematic partial section of an absorbent core according to an embodiment of the present invention.

Fig. 6 is a schematic section of a system suitable for carrying out the test method to visualize the backing sheet therethrough.

Fig. 7 is a schematic drawing of a graphic system with an image acquisition equipment suitable for carrying out the test method to visualize the backing sheet therethrough.

Fig. 8 is a schematic drawing of a weight used in the test method to visualize the backing sheet through it (front view).

Fig. 9 is a schematic drawing of a weight used in the test method to visualize the backing sheet through it (side view).

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Detailed description of the invention

Definitions

"Absorbent core" means a structure that is disposed between a top sheet and a backing sheet of a disposable diaper to absorb and hold the liquid received by the disposable diaper.

"Air felt" is used herein to refer to crushed wood pulp, which is a form of cellulose fibers (absorbent fibers).

"Diaper" refers to an absorbent article generally used by babies and by incontinent persons in the lower torso area surrounding the wearer's waist and legs and that is specifically adapted to receive and contain urine and fecal remains. For the present invention, the term "diaper" is considered to encompass "diaper panties."

"Diaper panties", herein, refers to disposable garments that have a waist opening and leg openings designed for baby or adult carriers. A diaper pant can be placed by inserting the user's legs into the leg openings and raising the diaper pant to approximately the bottom of the user's torso. A diaper pant can be previously formed by any suitable technique, including, but not limited to, joining parts of the article using seams that can be fixed repeatedly and / or that cannot be fixed repeatedly (e.g., sewing, stitching, adhesive bond, cohesive bond, fixative, etc.). A diaper pant can be pre-formed in any position along the perimeter of the article (e.g., be held laterally, fastened on the front of the waist). The term "panties-diaper" is also commonly referred to as "pre-cut diaper", "adjustable diaper," "diaper panties," and "panties."

"Disposable" is used in its usual sense in reference to an item that has been discarded or rejected after a limited number of uses in a variable period of time, for example, less than 10 uses, less than 5 uses, or less than 2 applications. A disposable absorbent article is discarded more frequently after a single use.

"Hot melt adhesive" herein refers to adhesives according to the description given in "Adhesion and Adhesives Technology: An Introduction" by Alphonsus V. Pocius (Hanser publishers Munich, 1997). In said document, a melt is defined as an adhesive applied in the molten state and which improves its strength after solidification.

"Non-elastic" herein refers to a backing sheet that is not recovered by more than 20% if subjected to the following test:

A rectangular piece of backing sheet material (such as a film or a nonwoven material or - if the backing sheet comprises a film and a nonwoven web - both materials taken together in the configuration in which they are used as the backing material) backsheet) that has a width of 2.54 cm and a length of 25.4 cm is held in a vertical position by holding the piece by its upper edge width of 2.54 cm along its full width. A force of 10 N is applied to the opposite lower edge along the full width of the material for 1 minute at 25 ° C.

Immediately after one minute, the length of the piece is measured while the force is still applied, and the degree of elongation is calculated by subtracting the initial length (25.4 cm (10 inches)) from the length measured after one minute.

Immediately after measuring the length of the rectangular piece, the force is removed and the piece is left flat on a table for 5 minutes (at 25 ° C) so that it can be recovered. Immediately after 5 minutes, the length of the piece is measured again, and the degree of elongation is calculated by subtracting the initial length (25.4 cm (10 inches)) from the length measured after 5 minutes.

Elongation after one minute during force application is compared to elongation once the piece has been laid flat on a table for 5 minutes. If the elongation is not recovered by more than 20%, the material or element is considered as "non-elastic".

"Strongly non-elastic" herein refers to a material or element, which is either "non-extensible" or that is not recovered by more than 10% if submitted to the set of tests detailed above for the "non-elastic".

A "nonwoven web" is a sheet or web, made of the fibers oriented in a certain direction or at random, joined by friction and / or cohesion and / or adhesion, excluding paper and products that are woven, knitted, inserted into strands , joined by seams that incorporate threads or filaments, or formed in felt by wet bending, with or without additional seams. The fibers can be of natural or artificial origin and can be raw material or continuous filaments or formed in situ. Commercial fibers have diameters ranging from less than about 0.001 mm to more than about 0.2 mm, and they have different shapes, such as short fibers (known as discontinuous or cut), single continuous fibers (filaments or monofilaments), untwisted beams of continuous filaments (bast) and twisted beams of continuous filaments

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(thread). Non-woven bands can be formed by many processes such as meltblown, spunbond, solvent spinning, electrowinning, carding and airborne. The non-woven bands can be joined by heat and / or pressure or they can be bonded together. The joint can be limited to some areas of the nonwoven web (punctual joint). The non-woven bands can also be hydroentangled or needle punctured. The weight of nonwoven bands is usually expressed in grams per square meter (g / m2).

"Super absorbent polymer particles" herein refers to polymeric particles substantially insoluble in water that can absorb at least 5 times their weight of a 0.9% aqueous saline solution, as measured by the retention capacity test. with centrifuge (Edana 441.2-01).

"Super absorbent polymer particles" refers to an absorbent polymeric material that is in the form of particles so that it can become fluid when dry.

Disposable diaper

Fig. 1 is a plan view of a disposable diaper 10 according to a particular embodiment of the present invention. The disposable diaper 10 is represented in its extended state, without contracting (i.e., without elastic induced contraction) and parts of the disposable diaper 10 are cut to more clearly show the underlying structure of the disposable diaper 10. A part of the disposable diaper 10 entering in contact with a carrier it is oriented towards the observer in Fig. 1. The disposable diaper 10 can generally comprise a frame 12 and an absorbent core 14 disposed on the frame 12.

The frame 12 of the disposable diaper 10 in Figure 1 comprises the main body of the disposable diaper 10. The frame 12 may comprise an outer cover 16 including an upper sheet 18 that can be permeable, and / or a backing sheet 20 that can be waterproof. The absorbent core 14 may be coated between the topsheet 18 and the backsheet 20. The frame 12 can also include side panels 22, folds 24 turns for the legs and a characteristic element 26 of elastic waist.

Each of the folds 24 turns for the legs and the characteristic elastic waist element 26 can typically comprise elastic elements 28 such as elastic strips. An end part of the disposable diaper 10 is configured as a front waist region 30 of the disposable diaper 10. An end part of the disposable diaper 10 is configured as a rear waist region 32 of the disposable diaper 10. An intermediate part of the disposable diaper 10 is configured as a crotch region 34 that extends longitudinally between the first and second waist regions 30 and 32. Waist regions 30 and 32 may include elastic elements that are wrapped around the wearer's waist to provide better fit and confinement (characteristic element 26 of elastic waist). The crotch region 34 is that part of the disposable diaper 10 which, when the disposable diaper 10 is used, is generally placed between the legs of the wearer.

The disposable diaper 10 is shown in Fig. 1 with its longitudinal axis 36 and its transverse axis 38. The periphery 40 of the disposable diaper 10 is defined by the outer edges of the disposable diaper 10, where the longitudinal edges 42 generally extend parallel to the longitudinal axis 36 of the disposable diaper 10 and the outer edges 44 extend between the longitudinal edges 42 generally parallel to the transverse axis 38 of the disposable diaper 10. The disposable diaper 20 may also include other features such as those known in the art, including panels of front and rear lugs, waist, elastic and similar characteristics to provide better adjustment, confinement and aesthetic characteristics.

To keep the disposable diaper 10 in place in the body of the wearer, at least a part of the first waist region 30 may be joined by the clamping member 46 to at least a part of the second waist region 32 to form leg opening / s and an article waist. To this end, according to certain embodiments, the disposable diaper 10 may be provided with a fastener system that can be closed again or alternatively may be provided in the form of a disposable diaper panty. When the absorbent article is a disposable diaper, it may comprise a fastener system that can be closed again attached to the frame to fix the disposable diaper with respect to the carrier. The fastening system may also include at least one fastening member 46 and at least one positioning zone 48. When the absorbent article is a disposable diaper pant, the article may comprise two side panels in each waist region 30, 32 attached to the frame along the longitudinal edges of the side panels facing the longitudinal axis 36. The panels The sides of the waist region 30 are additionally joined to the respective face panels of the back waist region 32 by their longitudinal edges oriented outwardly from the longitudinal axis 36 to form a panty.

A cross-section of Fig. 1 is shown in Fig. 2 along sectional line 2-2 of Fig. 1. Starting from the face facing the wearer, the disposable diaper 10 can comprise the top sheet 18 , the components of the absorbent core 14, and the backing sheet 20. The disposable diaper 10 may also comprise a collection system 50 disposed between the liquid permeable topsheet 18 and a face oriented to the carrier of the absorbent core 14. The collection system 50 may be in direct contact with the absorbent core.

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The collection system 50 may comprise a single layer or multiple layers (not shown), such as an upper collection layer oriented towards the wearer and a lower collection layer oriented towards the garment of the wearer. According to a particular embodiment, the collection system 50 can be operated so as to capture a liquid leak, such as a stream of urine. In other words, the collection system 50 can serve as a temporary reservoir of liquid until the absorbent core 14 can absorb the liquid.

In a particular embodiment, the collection system 50 may comprise chemically crosslinked cellulose fibers and / or nonwoven webs.

Absorbent core

The absorbent core of the present invention has a longitudinal direction with a longitudinal axis and perpendicular thereto is a lateral direction with a transverse axis. The longitudinal axis is substantially parallel to the longitudinal axis of the disposable diaper and the lateral direction is substantially parallel to the transverse axis of the disposable diaper. The absorbent core also has a front region, a posterior region and a crotch region between the foregoing and an opposite posterior frontal edge, and extending longitudinally along the lateral edges. The absorbent core may comprise a first and lower, and second and upper, carrier substrate and superabsorbent polymer particles located in the first carrier substrate or between the first and second carrier substrate. The superabsorbent polymer particles are immobilized by a first adhesive core.

The front part of the absorbent core represents one third of the absorbent core that extends from the leading edge of the absorbent core along the longitudinal axis towards the crotch region. The front area is located towards the edge of the front waist of the disposable diaper. The rear part represents a third of the absorbent core that extends from the rear edge of the absorbent core along the longitudinal axis towards the crotch region. The rear area is located towards the edge of the rear waist of the disposable diaper. The crotch area represents the remaining third of the absorbent core and extends between the front and rear areas. The full length of the absorbent core is defined by the longest extension of the absorbent core along, or parallel to the longitudinal axis of the absorbent core. The absorbent core of the present invention can be rectangular. In one embodiment, the crotch region of the stratified absorbent core has a narrower width than the front and rear regions of the absorbent core, while the leading and trailing edge of the absorbent core continues to form a straight line.

In one embodiment the superabsorbent polymer particles 66 are disposed on the first carrier substrate 64, and the first adhesive core 94 is disposed on the superabsorbent polymer particles 66. Typically, the first adhesive core 94 is a hot melt adhesive. In one embodiment, the first adhesive core 94 forms a fibrous layer that is at least partially in contact with the superabsorbent polymer particles 66 and partially in contact with the first carrier substrate 64. A second adhesive core (not shown) may be deposited on the first carrier substrate 64 before applying the superabsorbent polymer particles 66 to improve adhesion of the superabsorbent polymer particles 66 and / or the first adhesive core 94 to the first carrier substrate 64.

The first carrier substrate 64 can be sized such that, when the superabsorbent polymer particles 66 and the first 94 have been applied, the first carrier substrate 64 folds on itself with the superabsorbent polymer particles 66 and the first adhesive core 94 towards the interior and the first carrier substrate 64 surrounding the particles 66 of superabsorbent polymer and the first adhesive core. 94. The area of the first carrier substrate 64, which is retracted, may be free of particles 66 of superabsorbent polymer and the first adhesive core 94 before refolding. Alternatively, the area of the first carrier substrate 64, which is retracted, may also comprise superabsorbent polymer particles 66 and a first adhesive core, so that when folded, the two layers of superabsorbent polymer particles 66 overlap each other, where the first adhesive core is located between the two layers of superabsorbent polymer particles. The superabsorbent polymer particles 66 may be applied in clusters to constitute receiving areas 92 and joining areas 96, as explained in more detail below. Also, the first adhesive core 94 may only be applied in said areas, where the first carrier substrate 64 is folded. After folding, the first adhesive core 94 will also come into contact with the superabsorbent polymer particles 66 of the area, which is not folded, thus immobilizing the superabsorbent polymer particles 66 of this area.

Alternatively to refolding the first carrier substrate 64, the absorbent core 14 may also include a second carrier substrate 72. In a further embodiment, the absorbent core does not comprise a second carrier substrate. In this embodiment, the components of the disposable diaper 10 located at the top of the absorbent core 14 are in direct contact with the particles 66 of superabsorbent polymer and the first adhesive core 94.

The first carrier substrate 64, during the use of the disposable diaper 10, is oriented towards the garment of the wearer and the second optional carrier substrate 72, during the use of the disposable diaper, is oriented towards the wearer. The second optional carrier substrate 72 may be a nonwoven web or alternatively it may be a tissue paper. The first carrier substrate 64 can be a nonwoven web or alternatively it can be a tissue paper or a film. The first and second carrier substrate 64, 72 may be made of the same material or may be made of different materials. In embodiments where the first and second carrier substrate 64, 72 are both

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non-woven bands, said non-woven bands may be the same non-woven bands or may differ from each other, e.g. eg, with respect to its weight, hydrophilicity, air permeability or number and / or type of layers comprised by the nonwoven webs. The type of layers can be spun-bonded or blow-molded layers. The nonwoven webs may also be carded bands of cut fibers, and the carded bands may or may not comprise binder material. The non-woven bands can also be hydroentangled or needle punctured.

The absorbent core 14 may be substantially free of air felt. The absorbent core 14 typically comprises less than 5% by weight of air felt, more typically less than 2% by weight and more typically is free of air felt. The absorbent core does not include a collection system 50, an upper sheet 18, or a backing sheet 20 of the disposable diaper 10. In one embodiment, the absorbent core 14 will consist essentially of the first and optionally the second carrier substrate 64, 72, the 66 particles of superabsorbent polymer, the first adhesive core 94, and optionally the second adhesive core. "It consists practically of" in this respect means that these components constitute at least 98% by weight of the absorbent core, preferably at least 99% by weight.

"Area of superabsorbent polymer particles" herein refers to the area (of the carrier-oriented surface) of the absorbent core that is comprised of superabsorbent polymer particles. The areas adjacent to the longitudinal side edges and the areas adjacent to the front and rear side edges of the absorbent core may be free of superabsorbent polymer particles to allow the edges of the first carrier substrate 64 to be glued to the edges of the optional second substrate 72 ( or, in the absence of a second carrier substrate 64, the edges of the first carrier substrate can be attached to a layer that is above the absorbent core 14, such as a layer of the collection system 50). The absorbent core 14 comprises channels, that is to say areas that are substantially free of superabsorbent polymer particles 66 and that are not provided adjacent to the edges of the absorbent core 14 but in some other location. "Substantially free of superabsorbent polymer particles", herein, means that p. ex. Due to process-related reasons, a negligible small amount of superabsorbent polymer particles may be present in the gaps, so that it does not contribute to the overall functionality. The term "practically free of superabsorbent polymer particles" encompasses "free of superabsorbent polymer particles." However, for the present invention, the "superabsorbent polymer particle area" comprises at least 80% of the surface area of the absorbent core, preferably at least 85% or at least 90%.

"Distributed substantially continuously" herein means that within the area of the superabsorbent particle, the first carrier substrate 64 and the second optional carrier substrate 72 (or the first substrate and the layer provided on top of the absorbent core 14 towards the carrier, such as a layer of the collection system 50) are separated by a multiplicity of particles 66 of superabsorbent polymer. It is recognized that there may be accidental minimum contact areas between the first carrier substrate 64 and the second optional carrier substrate 72 (or the first carrier substrate 64 and the component provided at the top of the absorbent core 14 towards the carrier, such as a system 50) within the area of superabsorbent polymer particles. Such accidental contact areas are due to unintended manufacturing devices.

The absorbent core of the present invention may comprise - or may consist of - two layers. In Fig. 3 a first layer 60 of absorbent core is shown. Figure 4 shows an embodiment of an absorbent core, wherein the first and second layer 60, 62 of absorbent core has been combined with the absorbent core 14. Fig. 5 shows an embodiment of an absorbent core consisting of a single layer

In embodiments having a first and second absorbent core layer, the first layer 60 of the absorbent core may comprise the first carrier substrate 64 and a first layer of superabsorbent polymer particles 66, wherein the superabsorbent polymer particles 66 are immobilized by a first adhesive core 94. Optionally, the first layer 60 of the absorbent core may comprise a second adhesive core (not shown). A second adhesive core may be deposited on the first carrier substrate 64 before applying the superabsorbent polymer particles 66 to improve adhesion of the superabsorbent polymer particles 66 and / or the first adhesive core 94 to the first carrier substrate 64. The first core Adhesive 94 may be applied on the superabsorbent polymer particle layer as a fibrous layer, preferably such that a fibrous web is formed.

The second layer 62 of the absorbent core of said embodiments comprises a second carrier substrate 72 and a second layer of superabsorbent polymer particles 66, wherein the superabsorbent polymer particles 66 may be immobilized by a first adhesive core 94. Optionally, the second layer 62 of the absorbent core may comprise a second adhesive core (not shown). A second adhesive core may be deposited on the second carrier substrate 72 before applying the superabsorbent polymer particles 66 to improve adhesion of the superabsorbent polymer particles 66 and / or the first adhesive core 94 to the second carrier substrate 72. The first core Adhesive 94 may be applied on the superabsorbent polymer particle layer as a fibrous layer, preferably such that a fibrous web is formed.

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Once the first and second layers 60, 62 of the absorbent core have been formed, the two layers of the absorbent core are combined with their respective outwardly oriented carriers 64, 72 and located between the particles 66 of superabsorbent polymer 66 to constitute the absorbent core 14.

In one embodiment, an additional substrate (not shown) such as a tissue paper or nonwoven web is placed between the first and second layers of the absorbent core. However, it is preferred that none of these substrates be placed between the first and second layer of the absorbent core and that the first layer of superabsorbent polymer particles is separated from the second layer of superabsorbent polymer particles only the one fibrous layer of the first core adhesive.

Fig. 3 shows a single layer of absorbent core. The superabsorbent polymer particles 66 are deposited on the first carrier substrate 64 in clusters 90 of particles comprising receiving areas 92 and joining areas 96 between the receiving areas 94. The receiving areas 94 the first adhesive core 94 does not come into contact with the first carrier substrate 64 or the second optional adhesive core directly; the joining areas 96 are areas where the first adhesive core 94 comes into contact with the first carrier substrate 64 or the second optional adhesive core directly. The joining areas 96 contain little or no superabsorbent polymeric material 66. Elevated areas 94 and joining areas 96 may have a variety of shapes included, but not limited to, circular, oval, square, rectangular, triangular, and the like.

When the first adhesive core 94 is applied as a fibrous layer, the first adhesive core 94 entangles the particles 66 of superabsorbent polymer, and thereby stabilizes the particles. In a further aspect, the first adhesive core 94 binds to the carrier substrate 64 and thus fixes the superabsorbent polymer particles 66 to the carrier substrate 64. In another embodiment, the first adhesive core 68 can also penetrate to a certain extent inside of the carrier substrate 64, thereby providing additional immobilization and fixation.

As explained above, the first and second carrier substrates 64 and 72 can be adhered together with adhesive around the periphery to form a wrap around the superabsorbent polymer particles 66 to hold the superabsorbent polymer particles 66 within the core absorbent 14.

As shown more clearly in Fig. 4, the first and second layers 60 and 62 of the absorbent core combine to form the absorbent core 14.

The first and second layers 60 and 62 of the absorbent core may be combined with each other to form the absorbent core 14 with the layers of the absorbent core displaced so that the superabsorbent polymer particles 66 of the first carrier substrate 64 and the superabsorbent polymer particles 66 of the second carrier substrate 72 taken together are substantially continuously distributed throughout the area of the superabsorbent polymer particle. In a certain embodiment, the superabsorbent polymer particles 66 are substantially distributed continuously throughout the area of the superabsorbent polymer particle while the superabsorbent polymer particles 66 of the respective first and second layers of the absorbent core alone are distributed so discontinuous between the first and second carrier substrates 64 and 72 in the clusters 90. In a given embodiment, the layers of the absorbent core may be displaced so that the receiving areas 92 of the first layer 60 of absorbent core are oriented towards the areas Binding 96 of the second absorbent core layer 62 and receiving areas 92 of the second absorbent core layer 62 are oriented toward the joining areas 96 of the first absorbent core layer 60. When the receiving areas 92 and the joining areas 96 are properly disposed and sized, the resulting combination of superabsorbent polymer particles 66 is a substantially continuous layer of superabsorbent polymer particles across the area of the superabsorbent polymer particle of the absorbent core 14.

According to the present invention, the superabsorbent polymer particles are typically present in an amount greater than about 85% by weight of the absorbent core, or greater than about 90% by weight of the absorbent core, or greater than about 95% by weight of the absorbent core Also, the superabsorbent polymer particles may be present in more than 95% of the absorbent material comprised by the absorbent core. The absorbent core may comprise less than 5% air felt (ie cellulose fibers). Typical absorbent materials are superabsorbent polymer particles, air felt (ie cellulose fibers) and - less frequently used - absorbent foams. Typically, the absorbent core comprises 50 g / m2 to 2200 g / m2 of the superabsorbent polymer particles, 100 g / m2 to 1500 g / m2 or even 200 g / m2 to 1200 g / m2.

According to the present invention, the amount of superabsorbent polymer particles may or may not vary along the length of the absorbent core, typically with the absorbent core being profiled in its longitudinal direction. It has been found that for most disposable diapers, liquid discharge occurs predominantly in the front half of the disposable diaper. The front half of the absorbent core 14 should therefore comprise most of the absorption capacity of the absorbent core. Thus, the front half of the absorbent core 14 may comprise more than about 60% by weight of the total amount of superabsorbent polymer particles comprised by the absorbent core, or more than about 65% by weight, 70% by weight, 75% by weight. weight, 80% by weight, 85% by weight, or 90% by weight of the superabsorbent polymer particles.

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Typically, the first adhesive core can be used to immobilize at least partially the superabsorbent polymer particles in both a dry and wet state. The first adhesive core can be arranged almost uniformly within the particles of absorbent polymer in the form of particles between the superabsorbent polymer particles. However, typically the first adhesive core 94 may be provided with a fibrous layer that is at least partially in contact with the superabsorbent polymer particles 66 and partially in contact with the first carrier substrate 64 and -if the second is present substrate 72 optional carrier. Typically, the first adhesive core 94 forms a fibrous web over the superabsorbent polymer particles 66 of each layer of the absorbent core. As illustrated for example in Fig. 4, the particles 66 of superabsorbent polymer can be provided as a discontinuous layer, and a layer of first adhesive core 94 is laid on the layer of particles 66 and 74 of superabsorbent polymer, so that the first adhesive core 94 is in direct contact with the particles 66 of superabsorbent polymer, but also in direct contact with the surfaces 80 and 84 of the carrier substrates 64 and 72 oriented towards the particles 66 of superabsorbent polymer 66 of the absorbent core 14, at locations where the carrier substrates 64, 72 are not covered by the superabsorbent polymer particles 66. This provides a virtually three-dimensional structure to the fibrous layer of first adhesive core 94 which, in itself, is a virtually two-dimensional structure with a relatively small thickness with respect to length and width. In other words, the first adhesive core 94 undulates between the superabsorbent polymer particles 66 and the surfaces 80, 84 of the carrier substrates 64 and 72 oriented towards the superabsorbent polymer particles of the absorbent core 14.

The first adhesive core 94 can provide cavities for coating the superabsorbent polymer particles, and thus immobilize this material. In a further aspect, the first adhesive core binds to the substrate or carrier substrates and thus fixes the superabsorbent polymer particles to the substrate or carrier substrates. Of course, although the first core adhesives described herein provide improved immobilization in the wet state (i.e., immobilization of the superabsorbent polymer particles when the disposable diaper and therefore the absorbent core are at least partially moistened), these First core adhesives can also provide good immobilization of the superabsorbent polymer particles when the absorbent core is dry.

Superabsorbent polymer particles

The superabsorbent polymer particles can have varied shapes. The term "particles" refers to granules, fibers, scales, spheres, powders, platelets and other profiles and shapes known to persons skilled in the art of superabsorbent polymer particles. E.g. the particles may be in the form of granules or beads, with a particle size of from about 10 pm to about 1000 pm, preferably from about 100 pm to about 1000 pm, even more preferably from about 150 pm to about 850 pm and most preferably from about 150 pm to about 500 pm. In another embodiment, the superabsorbent polymer particles may be in the form of fibers, that is, elongated and needle-shaped superabsorbent polymer particles. In these embodiments, the superabsorbent polymer fibers have a smaller dimension (ie fiber diameter) of less than about 1 mm, usually less than about 500 pm, and preferably less than 250 pm to 50 pm. The length of the fibers is preferably from about 3 mm to about 100 mm. The fibers can also be in the form of a long filament that can be knitted.

Preferred superabsorbent polymer particles of the present invention are spherical type particles. According to the present invention and unlike fibers, "spherical type particles" have a longer and shorter dimension with a ratio of particles between the longest and shortest in the range of 1-5, where a value of 1 it would be equivalent to a perfectly spherical particle and 5 would allow some deviation from such a spherical particle.

The superabsorbent polymer particle materials useful in the present invention include different water insoluble but water swellable polymers capable of absorbing large amounts of fluids. Such polymeric materials are generally known in the art and include all those well known polymers used or considered useful in the context of disposable absorbent article technology.

The preferred polymeric materials for preparing the superabsorbent polymer particles are the slightly crosslinked polymers of partially neutralized polyacrylic acids and the starch derivatives thereof. The starch-like superabsorbent polymer particles are also encompassed in the present invention. Preferably, the superabsorbent polymer particles comprise 25% to 95% by weight, more preferably 50% to 80% by weight of crosslinked partially neutralized polyacrylic acids. Crosslinking makes the polymer substantially water insoluble and determines, in part, the absorbent capacity and removable polymer content characteristics of the superabsorbent polymer particles.

Although the superabsorbent polymer particles are preferably of a type (i.e., homogeneous), mixtures of polymers can also be used in the present invention. The superabsorbent polymer particles may also comprise mixtures with low levels of one or more additives, such as for example silica powder, surfactants, adhesives, binders, and the like. In addition, superabsorbent polymer particles may comprise a particle size gradient or may comprise a certain range of particle size.

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Many of the previously known superabsorbent polymer particles exhibit gel blocking. "Gel blocking" occurs when particles made of superabsorbent polymer materials are wetted and particles swollen in this way inhibit the transmission of fluids to other areas or regions of the absorbent structure. The wetting of these other regions of the absorbent core therefore takes place through a very slow diffusion process. For practical purposes, this means that the collection of fluids by the absorbent structure is much slower than the speed at which the fluids are discharged, especially in jet situations. Exhaust of the disposable diaper can happen well before the superabsorbent polymer particles of the absorbent core are even close to being fully saturated or before the fluid can diffuse or wick from the "blocking" particles to the rest of the absorbent core.

One way commonly used to reduce gel blocking is to manufacture the most rigid particles, which allows the superabsorbent polymer particles to retain their original shape creating or maintaining the hollow spaces between the particles. A well known method for increasing stiffness is covalently and / or ionically crosslinking the carboxyl groups exposed on the surface of the superabsorbent polymer particles. This method is usually called surface crosslinking.

First and second adhesive core

The first and second optional adhesive core comprised by the absorbent core is preferably a hot melt adhesive. In some non-preferred embodiments, the first adhesive core is a hot melt adhesive while the second adhesive core may be another type of adhesive. The average weight of the first together with the optional second adhesive core in the absorbent core may be 0.5 g / m2 to 30 g / m2, between 1 g / m2 and 15 g / m2, between 1 g / m2 and 10 g / m2 or even between 1.5 g / m2 and 5 g / m2.

The first adhesive core serves to at least partially immobilize the superabsorbent polymer particles of the absorbent core, in both a dry and wet state.

Without intending to impose any theory, it has been discovered that such hot melt adhesives may be the most useful for immobilizing the superabsorbent polymer particles, combining good cohesion and good adhesion behavior. Good adhesion can stimulate good contact between the hot melt adhesive and the superabsorbent polymer particles and the carrier substrates. Good cohesion reduces the likelihood that the adhesive will break, especially as a response to external forces and, especially, as a response to deformation. When the absorbent core absorbs liquid, the superabsorbent polymer particles swell and subject the hot melt adhesive to external forces. The hot melt adhesive will allow this swelling without breaking and without transmitting too much compression force, which would prevent particles of absorbent polymer in the form of particles from swelling.

According to the present invention, the hot melt adhesive may, as a whole, comprise a single thermoplastic polymer or a mixture of thermoplastic polymers having a softening point, determined by the ASTM D-36-95 "Ring and Ball" method. [ring and ball], in the range of 50 ° C to 300 ° C, or alternatively the hot melt adhesive may comprise at least one thermoplastic polymer together with other thermoplastic diluents such as adhesive resins, plasticizers and additives such as antioxidants .

In certain embodiments, the thermoplastic polymer typically has a weight average molecular weight (Pm) greater than 10,000 and a glass transition temperature (Tg) normally below room temperature (25 ° C), or less than 22 ° C, or less than 18 0C, or less than 15 0C. In some embodiments, Tg may be greater than 0 0C> Tg. In embodiments where the thermoplastic polymer has more than one Tg, the values given refer to the lower glass transition temperature. The thermoplastic polymer may also have a softening point, determined by the ASTm D-36-95 "Ring and Ball" method, in the range between 50 0C and 300 0C. In some embodiments, the Pm of the thermoplastic polymer is less than 10,000,000.

In some embodiments, typical concentrations of thermoplastic polymer in a hot melt adhesive are in the range of about 20% to about 40% by weight of the hot melt adhesive.

Examples of polymers are block copolymers (styrenics) including three ABA block structures, two AB block structures and radial block copolymer structures (AB) n, where the A blocks are non-elastomeric polymer blocks, typically comprising polystyrene, and the B blocks are unsaturated conjugated diene or (partially) hydrogenated versions thereof. Block B is typically isoprene, butadiene, ethylene / butylene (hydrogenated butadiene), ethylene / propylene (hydrogenated isoprene) and mixtures thereof.

Other suitable thermoplastic polymers that can be used are metallocene polyolefins, which are ethylene polymers that are prepared using single site or metallocene catalysts. Inside, at least one comonomer can be polymerized with ethylene to form a copolymer, terpolymer or a higher order polymer. Also applicable are amorphous polyolefins or amorphous polyalphaolefins (APAO) which are homopolymers, copolymers or terpolymers of C2 to Ce alphaolefins.

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In illustrative embodiments, the adhesive resin typically has a Pm of less than 5000 and a Tg normally above room temperature (25 ° C), typical concentrations of the adhesive resin in the melt are in the range of about 30% at about 60% by weight of the hot melt adhesive. In certain embodiments, the adhesive resin has a Pm greater than 1000.

The plasticizer has a low Pm, typically less than 1000 and a Tg below room temperature, with a typical concentration of about 0% to about 15% by weight of the hot melt adhesive. In certain embodiments, the plasticizer has a Pm greater than 100.

In certain embodiments, the first and / or second adhesive core is hot melt adhesive present in the form of fibers. In some embodiments, the fibers will have an average thickness of about 1 micrometer to about 50 micrometers, or about 1 micrometer to about 35 micrometers and an average length of about 5 mm to about 50 mm, or about 5 mm to about 30 mm .

The absorbent core may also comprise a second adhesive core that is not illustrated in the figures. The second adhesive core may be deposited on the carrier substrate before applying the superabsorbent polymer particles on the carrier substrate to improve adhesion of the superabsorbent polymer particles and the first adhesive core to the respective carrier substrate. The second adhesive core may also help immobilize the superabsorbent polymer particles and may be the same adhesive as the first adhesive core or may be different from the first adhesive core. The second adhesive core is also preferably a hot melt adhesive. An example of a second commercial adhesive core is H.B. Fuller Co. (St. Paul, MN), product number HL-1620-B. The second adhesive core can be applied to the substrate or carrier substrates by any suitable means, but, according to certain embodiments, it can be applied in grooves of a width of about 0.5 mm to about 1 mm apart from about 0.5 mm to about 2 mm

Joining the absorbent core to the backing sheet

If a disposable diaper is placed on a carrier, the disposable diaper will acquire a curved shape to fit the wearer (i.e., the diaper) is not flattened but folded, with the regions of the front and rear waist of the diaper applied against the waist of the carrier and diaper crotch region placed against the carrier crotch region). In addition, the diaper will be subjected to a certain degree of flexion along lines that are substantially parallel to the longitudinal axis of the diaper between the wearer's legs and in the direction of the front waist region. Said flexion results in torsion of the diaper, that is, the diaper protrudes outward in the region of the crotch and at least in part of the region of the front waist.

After placing the disposable diaper to a bending carrier, the surface areas of the disposable diaper are altered as follows, compared to a flattened diaper. While the upper surface facing the wearer (ie the top sheet) is disturbed and vertical, the bottom surface facing the garment (ie the backing sheet) is elongated. The same applies to the absorbent core within the disposable diaper: The upper surface oriented towards the wearer (such as the first and second upper carrier substrates) is disturbed and vertical, while the lower surface oriented towards the garment (such as lower first and second carrier substrates) is elongated.

In the vast majority of disposable diapers marketed today, the absorbent core comprises a significant amount of cellulose fibers (air felt). The superabsorbent polymer particles comprised in these absorbent cores are mixed with the cellulose fibers and the particles are therefore held in place in the interstices existing between the cellulose fibers. In general, no adhesive is used to immobilize superabsorbent polymer particles. As a whole, these absorbent cores have quite plastic characteristics. If such a diaper experiences the flexion described above when the disposable diaper is placed on a carrier, the material inside the absorbent core can compensate at least part of the disturbance of the upper surface and elongation of the lower surface by migration of cellulose fibers and the superabsorbent polymer particles within the core.

Also, when the disposable diaper is wetted and the superabsorbent polymer particles swell and expand, the superabsorbent polymer particles can swell to some extent within the interstices of the cellulose fibers. Thus, the increase in volume of the absorbent core as a whole is less than the increase in volume of the superabsorbent polymer particles because the dry absorbent core provides some free space to which the particles can expand.

In an absorbent core of the present invention, which comprises little or no air felt and where the superabsorbent polymer particles are immobilized by an adhesive, the absorbent core has much more elastic characteristics compared to the conventional absorbent core described above. Since the superabsorbent polymer particles are immobilized more strongly than the superabsorbent polymer particles that are simply mixed in a matrix of cellulose fibers, the superabsorbent polymer particles cannot migrate into the absorbent core when the disposable diaper is placed in a carrier. Thus, the surface bending

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upper oriented towards the wearer as well as the elongation of the lower surface oriented towards the garment is much more pronounced than in conventional disposable diapers containing air felt.

Also, as the disposable diaper is wetted, the superabsorbent polymer particles swell and expand. Contrary to the conventional absorbent core containing air felt, an absorbent core containing little or no air felt does not provide any 'free space' in the interstices between the cellulosic fibers to which the superabsorbent polymer particles can expand. Thus, the absorbent core as a whole will expand and swell much earlier (ie, much longer before reaching the absorption capacity limit of the absorbent core) and will expand much more compared to a conventional absorbent core. Said expansion increases the strain applied to the lower surface oriented towards the garment (such as the lower carrier substrate) of the absorbent core and, in turn, increases the strain applied to the backing sheet. Consequently, the bottom surface oriented towards the garment of the absorbent core as well as the backing sheet will also lengthen after wetting the diaper.

As a consequence of the elongation of the surface oriented towards the wearer, the absorbent core is firmly pressed against the backing sheet of the disposable diaper. After the absorption of urine and liquid feces, the absorbent core is stained and, due to the dense contact between the absorbent core and the backing sheet, the staining can be seen through the backing sheet, especially if the weight of the backing sheet material is low and / or if the backing sheet has little or no stamping. This transparency of the spots has a negative impact on the consumer's acceptance of the disposable diaper, as it is perceived as of poor quality. In addition, transparency is often interpreted as wetting, that is, it is perceived that the absorbent core is moistened with liquid, which is a sign that the absorbent core has reached its maximum capacity - when the diaper is really far from having reached its capacity maximum The backing sheet can also be perceived as wet after visual inspection of the disposable diaper.

In addition, after elongation and staining of the backing sheet, the backing sheet tends to combine and form wrinkles and tension lines. Customers interpret these lines of tension and wrinkles as signs that the absorption capacity of the disposable diaper is exhausted and that the diaper must be changed. This effect will take place long before the diaper reaches its actual absorption limit.

The inventors have discovered that the above-mentioned drawbacks can be reduced if the bond between the absorbent core and the backing sheet is altered: In disposable diapers containing conventional air felt, as well as in commercial disposable diapers that have little or no air felt (eg, Pampers "Active Fit" sold in Germany in May 2011), the absorbent core is adhesively bonded to the backing sheet on the entire surface oriented towards the core garment absorbent (therefore, e.g., the first substrate bearing the absorbent core). This does not necessarily mean that 100% of the surface area of the carrier substrate is coated with adhesive but that such adhesive, such as hot melt adhesive, may be applied in small spirals and these spirals are applied on the carrier substrate.

If the absorbent core is adhesively bonded to the backing sheet essentially over the total area of the absorbent core, the absorbent core cannot move and expand independently of the backing sheet. Accordingly, as the absorbent core expands after swelling of the superabsorbent polymer particles, the backing sheet will also expand.

It has been found that this drawback can be reduced if the absorbent core is not attached to the backing sheet on the entire surface of the absorbent core If the absorbent core is attached to the backing sheet only in some limited areas, and these areas are carefully and significantly selected, the formation of folds and wrinkles in the backing sheet can be reduced. Also, the transparency of urine stains in the absorbent core through the backing sheet can be reduced.

According to the present invention, the absorbent core is attached to the backing sheet in any of the following locations:

a) The absorbent core is attached to the backing sheet of the disposable diaper in joining areas adjacent to the front side edge and the rear side edge of the absorbent core and the absorbent core is not attached to the backing sheet in any other region; or

b) the absorbent core is attached to the backing sheet of the disposable diaper in the crotch region of the absorbent core in one or more joining area (s) at or adjacent to the longitudinal axis of the absorbent core, wherein the one or more of a junction zone (s) cover 0.2% to 3% of the total surface area of the absorbent core, and the absorbent core is not attached to the backing sheet in any other region; or

c) the absorbent core is attached to the backing sheet of the disposable diaper in the crotch region of the absorbent core in the joint areas adjacent to the longitudinal side edges of the absorbent core and the absorbent core is not attached to the backing sheet in any other region; or

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d) the absorbent core is attached to the backing sheet of the disposable diaper in combinations of any of the bonding areas defined in a) to c) and the absorbent core is not attached to the backing sheet in any other region.

If the absorbent core is attached to the backing sheet according to option a), the joining areas adjacent to the front side edge and the rear side edge of the absorbent core may be provided only at the corners of the absorbent core, leaving the rest of the area adjacent to the front side edge and the rear side edge of the absorbent core without joining the backing sheet. The "remaining area" refers to 70%, or 80% of the width of the absorbent core in the area adjacent to the front and rear side edges. The one or more junction zone (s) of option a) or d) may cover 0.2% to 3%, preferably 0.5% to 2%, or 0.5% to 1.5%, or from 0.2% to 1.5% or from 0.2% to 1% of the surface area of the absorbent core. These percentages refer to the totality of all joining areas taken together.

In embodiments according to option a), the absorbent core may be attached to the backing sheet in a joint area adjacent to the front side edge and in a joint area adjacent to the rear side edge of the absorbent core and may not be attached to the backing sheet in any other region. Alternatively, the absorbent core may be attached to the backsheet in two, three or more joint areas adjacent to the front side edge and in two, three or more joint areas adjacent to the rear side edge of the absorbent core and may not be attached to the backing sheet in any other region. In another alternative, the absorbent core may be attached to the backing sheet in a joint area adjacent to the front side edge and in two, three or more joint areas adjacent to the rear side edge of the absorbent core and not be attached to the backing sheet in any other region; or it may be attached to the backing sheet in two, three or more joint areas adjacent to the front side edge and in a joint area adjacent to the back side edge of the absorbent core and is not attached to the backing sheet in any other region .

In embodiments according to option c), the absorbent core may be attached to the backing sheet in a joint area adjacent to a longitudinal side edge and in a joint area adjacent to the respective opposite longitudinal side edge and may not be attached to the backing sheet in any other region. Alternatively, the absorbent core may be attached to the backing sheet in two, three or more joint areas adjacent to a longitudinal side edge and in two, three or more joint areas adjacent to the respective opposite longitudinal side edge of the absorbent core and may not be attached to the backing sheet in any other region. In a further alternative, the absorbent core may be attached to the backing sheet in a joint area adjacent to a longitudinal side edge of the absorbent core and in two, three or more joint areas adjacent to the respective opposite longitudinal side edge and may not be attached to the backing sheet in any other region.

If the absorbent core is attached to the backing sheet according to option b), the one or more joining area (s) in the crotch region may have a longitudinal direction substantially parallel to the longitudinal direction of the absorbent core and may have a lateral direction substantially parallel to the lateral direction of the absorbent core. The relationship between the longitudinal direction and the lateral direction of the one or more junction zone (s) may be 0.5 to 2.0, or 2.0 to 0.5, or 0.5 to 1, 0, or 1.0 to 0.5. The one or more junction zone (s) of option a) or b) cover 0.2% to 3%, preferably 0.5% to 2%, or 0.5% to 1.5%, or 0.2% to 1.5% or 0.2% to 1% of the surface area of the absorbent core. These percentages refer to the totality of all joining areas taken together. Also, if the absorbent core is attached to the backing sheet according to option b), the disposable diaper may also comprise a moisture indicator where the moisture indicator is located between the absorbent core and the backing sheet in at least one of the one or more junction zone (s) in the crotch region of the absorbent core at or adjacent to the longitudinal axis of the absorbent core.

The expression "adjacent to the front lateral edge and the posterior lateral edge of the absorbent core", herein, means a distance less than 15%, or less than 10%, or less than 5% (based on the total length of the core absorbent) inwards, starting from the front side edge (for the adjacent joint area (s) to the front side edge) and rear side edge (for the adjacent joint area (s) ) to the posterior lateral edge), respectively and extending along or parallel to the longitudinal axis of the absorbent core towards the crotch area.

The expression "adjacent to the longitudinal axis of the absorbent core", herein, means that the junction zone is either in the longitudinal axis or at a distance of less than 15%, or less than 10%, or less than 5% (based on the total width of the absorbent core) from the longitudinal axis in the direction of the left or right longitudinal lateral edge. In embodiments that have more than one joint zone adjacent to the longitudinal axis of the absorbent core, the joint zones may be at a distance of less than 15%, or less than 10%, or less than 5% (based on the total width of the absorbent core) from the longitudinal axis in the direction of the left or right longitudinal lateral edge.

The term "adjacent to the longitudinal side edges of the absorbent core" herein means a distance less than 15%, or less than 10%, or less than 5% (based on the total width of the absorbent core) inwardly. , starting from the left and right longitudinal axis, respectively, and extending along or parallel to the transverse axis of the absorbent core in the direction of the crotch area.

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The total surface area of the absorbent core is defined by the x and y dimension of the absorbent core. Any possible unevenness of the surface and irregularities in the thickness (that is, in the z-direction) is not taken into account. The x, y dimension of the absorbent core is determined while the absorbent core remains flat on a table without tension or deformation applied thereon (this also applies to potentially extensible absorbent cores). If needed, elements that contract elastically that would otherwise apply strain to the absorbent core can be carefully removed before laying the flat absorbent core on a table.

The binding of the absorbent core to the backing sheet according to any of the options a) to d) above, the absorbent core, while expanding by liquid absorption, can move with respect to the backing sheet, so that the absorbent core can expand widely independently from the backing sheet and without forcing the backing sheet to expand together with the absorbent core. Thus, the formation of wrinkles and tension lines on the backing sheet can be reduced. Also, the transparency of urine stains through the backing sheet can be reduced (since the absorbent core is not held as closely against the backing sheet as in embodiments in which the absorbent core is attached to the sheet backup for the entire area of the absorbent core). It is believed that this is due to the formation of a small air cushion between the absorbent core and the backing sheet, which cannot be formed in areas, where the absorbent core is closely attached (eg by adhesive) to the backing sheet. To reduce transparency, it is believed that a very small air cushion is sufficient. To visualize the reduction of transparency, the test method defined below can be used. This test method allows a qualitative visualization with the naked eye (that is, without the need for a microscope or the like).

In the disposable diapers of the present invention, the top sheet may be sealed to the backing sheet along the perimeter of the top sheet and backing sheet, that is outside the areas where the absorbent core is fitted between the top sheet and the backing sheet. To allow the absorbent core to expand between the top sheet and the backing sheet, the top sheet can be sealed to the backing sheet at a distance away from the perimeter of the absorbent core, especially in the transverse direction, i.e. along the longitudinal side edges of the absorbent core. The joint between the top sheet and the backing sheet along the longitudinal side edges of the absorbent core may be such that the width of the absorbent core is less than 90%, preferably less than 85% of the width between the joints of the longitudinal side edges between the top sheet and the backing sheet. If the width of the absorbent core and / or the width between the joints of the longitudinal side edges of the topsheet and the backing sheet varies along the length of the disposable diaper, the width of the absorbent core may be less than 90% , preferably less than 85% of the width between the joints of the longitudinal side edges between the top sheet and the backing sheet at each point along the length of the disposable diaper.

Joining the absorbent core to the backing sheet in the joint areas adjacent to the front side edge and to the rear side edge of the absorbent core or in joint areas adjacent to the longitudinal side edges of the absorbent core has the advantage that the absorbent core is not It can be twisted or even rolled into the disposable diaper, as it stays in place for more than one location. This is especially advantageous in certain manufacturing processes where the individual absorbent cores are deposited in an endless band of backing sheet material (which is cut into individual backing sheets only at a later stage of the manufacturing process). The top sheet is placed on top of the absorbent core only after the absorbent core has been placed on the endless backing sheet material, typically in the form of an endless band of top sheet material, which is Cut into individual top sheets at a later stage along with the backing sheet. Thus, at a certain stage, the absorbent core is arranged in the upper part of the backing sheet without any overlapping component. The absorbent core, in addition to being attached to the endless band of backing sheet material in the bonding areas, is typically clamped onto the backing sheet by vacuum, below the backing sheet. However, at this stage, there is a risk that the absorbent core rises from the backing sheet especially in high speed manufacturing processes. Thus, when the absorbent core is attached to the backing sheet in more than one junction zone, as in the case of option a), c) and d) defined above, a reduced risk of the absorbent core rising is achieved. compared to option b), where the absorbent core is attached only to the backing sheet by one location.

However, joining the absorbent core to the backing sheet only in one location is however possible, if the manufacturing process is conveniently adapted (ie high vacuum, lower manufacturing line speed, or joining the absorbent core and the top sheet on the backing sheet at the same time). Joining the absorbent core to the backing sheet according to option b), that is only in a joint area, has the advantage that the expansion of the wet absorbent core is not impeded parallel to the longitudinal axis and parallel to the axis cross section of the absorbent core.

Once the top sheet has been placed on top of the absorbent core, the top sheet can be sealed to the backing sheet around the perimeter of the top sheet and the backing sheet, which can be made before or after trimming the upper sheet material and endless backing sheet in individual upper and lower sheets. Also, the topsheet can be attached to the absorbent core once the topsheet has been placed over the absorbent core.

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As the transparency is reduced, the present invention allows the use of backing sheet materials with a lower weight. The backing sheet of the disposable diaper of the present invention may consist of a film and optionally one or more nonwoven webs. The weight of the backing sheet, including the film and optional nonwoven webs, is less than 50 g / m2, or 25 g / m2 to 50 g / m2. The film (without the non-woven bands) has a weight of 10 g / m2 to 20 g / m2. Optional non-woven bands may have a weight less than 40 g / m2, or 10 g / m2 at 30 g / m2, or 10 g / m2 at 25 g / m2 (in embodiments that have more than one non-woven band , these values represent the sum of all nonwoven bands taken together).

Also, according to the present invention, the backing sheet may be white and have a stamped zone (of non-white colors) less than 50%, or less than 30% of the area that is coincident with the front region and the region of the crotch of the absorbent core.

The backing sheet of the disposable diaper of the present invention is not elastic. Non-elastic materials are generally less expensive compared to elastic materials, and since the absorbent core can expand independently of the backing sheet to some extent, it is not necessary for the backing sheet to be elastic. The backing sheet of the present invention may be strongly non-elastic.

The absorbent core may be attached to the top sheet of the disposable diaper. Since the topsheet is typically only attached to the backsheet at the perimeter of the topsheet and the backsheet, said bonding to the topsheet will not adversely affect the advantages of the present invention, especially the reduced transparency and reduced wrinkle formation and tension lines on the backing sheet. The absorbent core may be attached to the topsheet in at least the front region and the crotch region of the absorbent core. The absorbent core may be attached directly to the topsheet. Alternatively, in disposable diapers having a collection system between the top sheet and the absorbent core, the absorbent core may be attached to the collection system, which in turn is attached to the top sheet. The connection of the absorbent core to the topsheet or collection system can be carried out in an adhesive manner, for example by hot melt adhesive.

The binding of the absorbent core to the backing sheet according to the present invention can be done with an adhesive preferably a hot melt adhesive. The joint is directly between the absorbent core and the backing sheet. If the absorbent core has a first carrier substrate, the joint is between the surface oriented towards the garment of the lower carrier substrate and the surface oriented towards the carrier of the backing sheet.

The absorbent core of the present invention comprises one or more channels, that is to say areas that are substantially free of superabsorbent polymer particles and that are not provided adjacent to the edges of the absorbent core but in some other location. "Substantially free of superabsorbent polymer particles", herein, means that p. ex. Due to process-related reasons, a negligible small amount of superabsorbent polymer particles may be present in the gaps, so that it does not contribute to the overall functionality. The term "practically free of superabsorbent polymer particles" encompasses "free of superabsorbent polymer particles." The channels can be provided in the crotch region and / or in the frontal region of the absorbent core. The channels are lengthened and can have a ratio between width and length of 1 to 20, or 1 to 15, or 1 to 10, or 1 to 5, or 1 to 3. The channels can be straight or curved. Such channels can additionally help improve the comfort of the disposable diaper, that is, the diaper is better suited to the wearer. This can further help reduce the tension lines and wrinkles of the backing sheet described above. The junction zones, where the absorbent core is attached to the backing sheet, is preferably outside the area (s) that is provided with the one or more channels. The channels may not extend along the front and rear side edges and the longitudinal edges of the absorbent core.

The absorbent core of the present invention may additionally have a first carrier substrate, which is the substrate of the absorbent core that rests directly on top of the backing sheet. Since the absorbent core comprises one or more channels, the first carrier substrate may be water permeable (at 25 ° C and 50% RH) (such as a tissue paper band or a water permeable nonwoven web). In such embodiments, a certain amount of liquid (urine) can penetrate through the full thickness of the absorbent core and can be distributed over the space between the absorbent core and the backing sheet. Thus, the liquid distribution can be improved as the liquid is distributed between the absorbent core and the backing sheet to other more remote areas where it can be absorbed by the absorbent core. Taken together with the joining areas of the present invention, where the absorbent core is attached to the backing sheet and is left unbound to the backing sheet by any other region, the liquid between the absorbent core and the backing sheet can disseminate practically without obstructions. However, in these absorbent cores, the size of the one or more channels must be carefully selected to ensure that the amount of liquid that passes through the thickness of the absorbent core in the space between the absorbent core and the backing sheet is not too large. .

Test method to visualize backing sheet transparency

This method visualizes the transparency of the spots through the backing sheet of a disposable diaper. The test can be carried out with disposable diapers of different designs and extension of the joint between the absorbent core and the backing sheet to qualitatively visualize the differences. Loading protocol

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used is for disposable diapers typically designed for carriers with a weight in the range of 8 to 13 kg ± 20% (such as Pampers “Active Fit”, Size 4 or other Pampers baby diapers Size 4, Huggies baby diapers Size 4 and diapers for babies of Size 4 of other commercial brands).

Device charging protocol

The test apparatus is shown in Figure 6 and comprises a hole 111 made of polycarbonate (eg Lexan®) with a nominal thickness of 12.5 mm (0.5 inches). The hole 111 comprises a horizontal rectilinear base 112 having a length of 508 mm (20.0 inches), and a width of 152 mm (6.0 inches). Two rectilinear vertical sides with 113 64 mm (2.5 inches) high x 508 mm (20 inches) in length are fixed to the long edges of the base 112 to form a U-shaped hole 111 that is 508 long mm (20.0 inches), an internal width of 152 mm (6.0 inches), and an internal depth of 51 mm (2.0 inches). The front and rear ends of hole 111 are not closed.

A block 114 of open-cell polyurethane foam with dimensions 508 x 152 x 25 mm wrapped in polyethylene film and placed at the bottom of the hole 111 so that the edges of the foam 114 and the hole 111 are aligned, and the top surface of the polyethylene film is smooth and free of seams, wrinkles or imperfections. Polyurethane foam 114 has a compression module of 3.3 kPa (0.48 psi). A reference line is drawn across the width of the top surface of the 152 mm (6.0 inch) polyethylene shell from one end (the leading edge) parallel to the transverse center line using an indelible marker.

A rectilinear upper polycarbonate plate 115 has a nominal thickness of 12.5 mm (0.5 inches), a length of 508 mm (20.0 inches), and a width of 146 mm (5.75 inches). A hole of 51 mm (2.0 inches) in diameter is drilled in the center of the upper plate 115 (i.e. the center of the hole is located at the intersection of the longitudinal and transverse axes of the upper surface of the upper plate 115 ). A polycarbonate test tube 116 with an external diameter of 51 mm (2.0 inches), an internal diameter of 37.5 mm (1.5 inches) and a height of 102 mm (4.0 inches) is glued in the hole of the upper plate 115 so that the lower edge of the test tube 116 is in contact with the lower surface of the upper plate 115 and the test tube 116 protrudes vertically 89 mm (3.5 inches) above the upper surface of the plate upper 115, and the joint between the test tube 116 and the upper plate 115 is sealed. A cavity 117 with a height of 2 mm and a diameter of 44.5 mm (1.75 inches) is machined at the lower inner edge of the specimen 116. Two holes of 1 mm in diameter are drilled at an angle of 45 ° from the upper surface of the upper plate 115 so that the holes intersect the inner surface of the specimen 116 immediately above the cavity 117 and are on opposite sides of the specimen 116 (i.e. 180 ° apart). Two stainless steel wires 118 with a diameter of 1 mm are glued to the holes tightly, so that one end of each wire is in contact with the inner wall of the cylinder and the other end protrudes from the top surface of the plate upper 115. These wires are now referred to as electrodes hereinafter. A reference line is drawn along the width of the upper plate 115 152 mm (6.0 inches) from the leading edge parallel to the transverse center line. The upper plate unit 1415 / test tube 116 has a weight of approximately 1180 grams.

Two steel weights are also needed, each weighing 0.9 kg and measuring 127 mm (5 inches) wide, 50 mm (1.97 inches) deep and approximately and 16 mm (0.63 inches) in length. height.

Process

All tests were performed at 23 ± 2 0C and 35 ± 15% relative humidity.

The polycarbonate hole 111 containing the wrapped foam block 114 is placed on a suitable horizontal flat surface. A disposable absorbent product is removed from its container, and the elastics are trimmed at appropriate intervals to allow the product to remain flat. The product is accurately weighed to ± 0.1 grams on a suitable tabletop scale, and then placed on the foam block 114 wrapped in the collection equipment, with the front waist edge of the product aligned with the marking of reference on the polyethylene cover. The product is centered along the longitudinal centerline of the equipment with the top sheet (body face) of the product facing up and the edge of the back waist facing the back of the foam block 114. The top plate 115 is placed on top of the product, with the protruding cylinder facing up. The drawn reference is aligned with the edge of the front waist of the product, and the rear end of the upper plate 115 is aligned with the rear edge of the foam block 114. Then, the two 0.9 kg weights are gently deposited on the upper plate 115 so that the weight of each weight is parallel to the transverse center line of the upper plate, and each weight is 83 mm (3, 25 inches) from the leading or trailing edge of the top plate 115.

A suitable electrical circuit is connected to the two electrodes to detect the presence of electrically conductive fluid between them.

A suitable pump; p. ex. Model 7520-00 supplied by Cole Parmer Instruments, Chicago, USA UU., Or equivalent; is adjusted to discharge a 0.9% aqueous solution of sodium chloride mass through a flexible plastic tube having an internal diameter of 4.8 mm (3/16 inches), e.g. ex. Tygon® R-3603 or

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equivalent. The 0.9% NaCl solution is stained with Indigo carmine (Ci6H8N2Na2OeS2) from Merck (104724 Indigocarmin C.I. 73015), using 40 mg per liter of 0.9% NaCl solution. The end portion of the tube is held vertically so that it is centered within the specimen 116 attached to the top plate 115 with the discharge end of the tube facing down and located 50 mm (2 inches) below the top edge of the test tube 116. The pump is operated with a timer that is precalibrated to discharge a 90.0 cm3 (90.0 ml) jet of 0.9% saline at a rate of 15 cm3 / s (15 ml / s ).

The pump is activated and the timer starts immediately during activation. The pump supplies 90.0 cm3 (90.0 ml) of the 0.9% NaCl solution to test tube 116 at a rate of 15 cm3 / s (15 ml / s), and then stops. As the test fluid is introduced into the specimen 116, it typically accumulates in the upper part of the absorbent structure to some extent. This fluid completes an electrical circuit between the two electrodes of the test tube. After supplying the jet, the meniscus of the solution decreases as the fluid is absorbed into the structure. When the electrical circuit is broken by the absence of free fluid between the electrodes of the specimen, the time is recorded.

The capture time of a specific jet is the time interval between the activation of the pump to supply said jet and the moment when the electrical circuit is broken.

Four jets were supplied to the product in this way; Each jet measures 90.0 cm3 (90.0 ml) and is supplied at 15 cm3 / s (15 ml / s). The time interval between the beginning of each jet is 300 seconds.

Image acquisition equipment (for optional use in stage 10 of sample preparation and setup)

Image acquisition hardware

The image acquisition hardware consists of a computer and lighting bar 213 containing a digital camera 211, such as a Fuji HC2500 (211) or Sony DFW-X700 (211). The color calibration chart is a conventional color card measuring 22 cm x 28 cm (8.5 inches x 11 inches) Gretag-Macbeth, and two 212 lights.

Peripheral connection

The Fuji HC2500 camera has a PCI interface card installed in the PCI 2 slot of the computer. The Sony DFW-X700 connects to any Firewire port (IEEE-1348) of the computer.

Lighting bar

Lighting bar 213 is shown in Figure 7. Light 212 must meet the requirements of D65 such as OSRAM OSDULUXL36W12 or equivalent (CC / Kelvin temperature 5127 0C (5400 K); daytime color; CRI 90CRI). The angle a between the base 214 and the lighting bar 213 is 70 °. The angle p between the lighting bar 213 and the light 212 should be adjusted to achieve uniform illumination of the base 214.

Sample preparation and configuration

1. Directly after all the liquid has been absorbed in the diaper, the diaper must be removed from the test equipment.

2. Immediately open the product with the top sheet facing up.

3. Unfold the diaper and tear the diaper elastics along the continuous link.

4. Arrange the flat and rectangular diaper, with the top sheet facing down on the surface of the board without any crease.

5. Hold the edge of the front waistband of the diaper with one hand against the table surface to prevent any movement.

6. Gently place the weight 312 (9 kg and measure 148 mm (5.83 inches) wide, 38 mm (1.5 inches) deep, and approximately 101 mm (3.98 inches high)) in the edge of the front waist of the diaper with an angle of 45 ° or less, on the edge of the front waist of the baby diaper near his hand. The face of the weight 312 should be parallel to the transverse axis of the diaper. Now, slide the weight toward the edge of the diaper's back waist, maintaining the angle of 45 ° or less so that the weight slides over the diaper only by one of its edges 313, holding the weight with the handle 311. This It should take approximately 1 to 2 seconds for a diaper that has a longitudinal extension of 400 mm to 500 mm.

7. Take the front and waist edges of the diaper, raise and fold the diaper so that it forms a circle. During this procedure, the diaper crotch region should remain in contact with the table.

8. Release the ends of the diaper, and arrange the flat and rectangular diaper with the top sheet facing down on the surface of the board without any crease.

9. Lightly touch the surface of the backsheet with your flat hand and move your hands three times 5 gently in the transverse direction (ie parallel to the transverse axis of the diaper) forward and backward.

10. Visually inspect the diaper with the naked eye: The areas where the backing sheet sticks tightly to the absorbent core are recognized as darker areas where the dyed absorbent core shines through the backing sheet to some extent. The areas where the backing sheet has separated

10 of the absorbent core can be identified by its lighter color. The difference between a backing sheet with large areas adhesively bonded to the core and a backing sheet with only small areas adhesively bonded to the core is quickly evident typically.

To archive the result, diapers can be photographed using the equipment described in the “Image acquisition equipment

Claims (10)

10 fifteen twenty 25 30 2. 35 3. 40 45 4. 5. fifty 6. 55 7. 8. 60 Disposable diaper (10) comprising a backing sheet (20), an upper sheet (18) and in between of the above an absorbent core (14), the absorbent core (14) having a longitudinal direction with a longitudinal and perpendicular axis thereto a lateral direction with a transverse axis, the absorbent core also having a leading region, a posterior region and a crotch region between means and a frontal lateral edge, an opposite posterior lateral edge, and longitudinally extending lateral edges, wherein the absorbent core comprises superabsorbent polymer particles (66, 74), the superabsorbent polymer particles being immobilized by a first adhesive core (94), and wherein the absorbent core comprises one or more elongate channels that are free of particles of superabsorbent polymer, where a) said absorbent core (14) is attached to the backing sheet (20) of the disposable diaper (10) in areas adjacent to the front side edge and the rear side edge of the absorbent core and where the absorbent core (14) it is not attached to the backing sheet (20) in any other region; or b) said absorbent core (14) is attached to the backing sheet (20) of the disposable diaper (10) in the crotch region of the absorbent core in one or more of a joint area (s) at or adjacent to the axis longitudinal of the absorbent core, where the one or more of a junction zone (s) cover 0.2% to 3% of the total surface area of the absorbent core, and where the absorbent core (14) is not attached to the backsheet (20) in any other region; or c) said absorbent core (14) is attached to the backing sheet (20) of the disposable diaper (10) in the crotch region of the absorbent core in joint areas adjacent to the longitudinal side edges of the absorbent core and wherein the absorbent core (14) is not attached to the backing sheet (20) in any other region; or d) said absorbent core (14) is attached to the backing sheet (20) of the disposable diaper (10) in combinations of any of the joining areas of a) to c) and where the absorbent core (14) is not attached to the backing sheet (20) in any other region; Y wherein the backing sheet (20) is non-elastic and consists of a film and optionally one or more nonwoven webs and where the weight of the backing sheet including the film and the optional nonwoven webs is less than 50 g / m2 and where the film has a weight of 10 g / m2 to 20 g / m2. The disposable diaper (10) of claim 1 a), wherein the joining areas adjacent to the front side edge and the rear side edge of the absorbent core (14) are provided at the corners of the absorbent core, leaving the rest of the adjacent area to the front side edge and the rear side edge of the absorbent core without joining the backing sheet (20). The disposable diaper (10) of claim 1 b), wherein the one or more of a junction zone (s) in the crotch region have a longitudinal direction substantially parallel to the longitudinal direction of the absorbent core and a lateral direction substantially parallel to the lateral direction of the absorbent core, wherein the relationship between the longitudinal direction and the lateral direction of the one or more of a junction zone (s) is 0.5 to 2 The disposable diaper (10) of claim 1 b) or d) or of claim 3, wherein the disposable diaper further comprises a moisture indicator and wherein the moisture indicator is placed between the absorbent core (14) and the sheet (20) backup in at least one of the one or more of a junction zone (s). The disposable diaper (10) of any of the preceding claims, wherein the backing sheet (20) is strongly non-elastic. The disposable diaper (10) of any of the preceding claims, wherein the absorbent core (14) is attached to the topsheet (18) at least in the front region and in the crotch region of the absorbent core. The disposable diaper (10) of any of the preceding claims, wherein the absorbent core (14) comprises less than 5% air felt. The disposable diaper (10) of any of the preceding claims, wherein the absorbent material comprised of the absorbent core (14) comprises more than 95% particles (66, 74) of superabsorbent polymer. The disposable diaper (10) of any of the preceding claims, wherein the absorbent core (14) comprises a first and second carrier substrates (64, 72), and wherein the superabsorbent polymer particles (66, 74) are provided between the first and second carrier substrate (64, 72). 10. The disposable diaper (10) of any of the preceding claims, wherein the first adhesive core (94) is a hot melt adhesive. 11. The disposable diaper (10) of claim 1, wherein the one or more channels are provided in areas 5 different to the zone (s) of union. 12. 10 13. The disposable diaper (10) of any of the preceding claims, wherein the absorbent core (14) is attached to the backing sheet (20) by means of an adhesive. The disposable diaper (10) of claim 12, wherein the adhesive is hot melt adhesive.